Process for the preparation of ferric nitroso dimethyl dithiocarbamate



PROCESS FOR THE PREPARATION'D I NI'I'ROSO DIlVIETI-IYL DITHI OCARBAMATE IrvingGibbs, Norwalk, Conm, assignor to R. T; Vanderhilt, Company, Inc.,,New ork',N.Y., a corporation ofNe wYork j I No, Drawing. Filed A... 20, 1959, set. No. 807,321 13 Claims. or. 260-5439) thiocarbamate is reacted with asoluble ferrous saltand a nitrite saltin. acidj liqu id medium to form a-slurry of ferric nitroso dimethyl dithiocarbamate fin'jjthe liquid medium, after which'the excessi'acid in th'el system is parf tially neutralized and the solids are filtered and washed to remove soluble impurities. The product, however, contains about 30% of tetramethylthiuram disulfide' based on the weight of ferric nitroso dimethyl dithiocarbamate. The tetramethyl compound, although desirable in small amounts because it enhances and promotes the fungi-' Bunnie.

2,972,625 Patented Feb. 21, 1961 2 lower amounts of tetramethylthiuram disulfide. For the purpose of convenience, however, it may be preferred to maintainthe reaction system at room temperature and such operation is satisfactory for producing the desired product.

Since all of the nitrogen oxides are generally volatile substances, there is a certain amount that may or will be lost by evaporation. Accordingly, to realize optimum yields weprefer touse 10% or even more excess nitric oxide over that that is required by the stoichiometry of the reaction. As a source of the iron salt I preferably use a soluble ferrous-salt such as hydrated ferrous sulfate. However, other soluble ferrous salts can be used if desired.

The dimethyl dithiocarbamate will usually be added in the form of a sodium salt. This can be made in the known manner of reacting stoichiometric amounts ofv sodium hydroxide, dimethyl amine and carbon disulfide.

In place of sodium dimethyl dithiocarbamate there canbe used potassium dimethyl dithiocarbamate or other water soluble salts of dimethyl dithiocarbamic acid.

In one type of procedure for preparing the ferric nitroso dimethyl dithiocarbamate, a dilute solution of sodium dimethyl dithiocarbamate and sodium nitrite is prepared.

In a separate vessel a solution of ferrous sulfate and sulfuric acid islprepared. The ferrous sulfate solution is added slowly with" good agitation to the sodium dimethyl dithiocarbamate-sodium nitrite solution. The pH is then determined to make certain that it is about 6 or below, preferably between 5 and 6. After stirring for a period of time a sufficient amount of sodium hydroxide is added to neutralize the excess acid and furthermore we carry the pH well above the neutral point, i.e., 9 or cidal properties .of ferric nitroso dimethyl dithiocarbamate, has certain disadvantagesin that it may be toxic.

if it is present in the fungicidal composition -in--large amounts.

Accordingly, an object of the present invention is: to prepare ferric nitroso dimethyl dithiocarbamate by improved procedure which makes possible a reduction and more rigorous control "of the content of tetramethylthiuram disulfide.

1 Other objects andadvanta'gs of the invention: will appear fromithe followingidescription.

In accordai ce wiih the presenti'iention, I follow the general procedure stated above for preparing the desired compound but in addition I increase the pH of the slurry of ferric nitroso dimethyl dithiocarbamate in the liquid mediumto avalue-well above the neutral .point, i.e., at least, to about-9 andthereafter filter the solids from the liquid in;- the slurryand ,wash thesolids to remove soluble impurities. r I

,The nitric oxide will usually be generated in the system byreaction between jagnitrite salt such as sodium nitrite and ania'cid such as, sulfuricacid. The amount of acid inthe system should preferably be such as to reduce the pH to j6 or below, preferably in the range of 5 to 6 during the reaction between the dimethyldithiocarbamate, the ferrous salt and the nitric oxide. Furthermore, it is known that nitrous acid, which is formed by the reaction between the nitrite and the sulfuric acid, will decompose into nitric oxide or into other products depending upon the conditions prevailing in the system, for example the temperature of the liquid medium and the concentration of thereactants Accordingly, for the purpose of the above. The aqueous slurry obtained is filtered and washed until it is free of all soluble salts. The product is dried at a temperature preferably not exceeding 140 F. The dried product may be ground in an inert atmosphere such as carbon dioxide or nitrogen to prevent loss of nitric oxide and/or spontaneous combustion.

The reason for increasing the pH of the slurry well above the neutral point is to prevent the formation of the cationic form of ferric nitroso dimethyl dithiocarbamate, which is brown in color. The anionic form,

"which is the desired product, is green. Transference presentinvention those conditions are maintained that bringtabqut the formation of nitric oxide.

It is known thatthe nitric oxide is more soluble in cold water and accordingly, for reactions of this type, temperatures somewhat lower than room temperature, i.e., 32f to -60; F. .are frequently employed, Furthermore, the lower temperatures generally favor the formation of studies have made this evident. See Mueller, Inorganic Chemistry-An Advanced Textbook, John Wiley & Sons, Inc., New York, 1952, page 603. The true nature of these materials, however, is not known. The higher pH also retardsthe formation of tetramethylthiuram disulfide by completely neutralizing any residual nitric oxide.

Inv an alternative procedure, a solution of ferrous sulfate and sufficient sulfuric acid to aid in dissolving the ferrous sulfate is added slowly to an aqueous solution of sodiumdimethyl dithiocarbamate (in the absence of nitrous acid). This causes the precipitation of a lightbrownislurry of ferrous dimethyl dithiocarbamate. The solution of sodium nitrite in water isthen'added to the. slurry'withv stirring. The pH is maintained between 5 and 6 at all times by adding further amounts of sulfuric acid. Stirring is continued until the reaction is complete and sodium hydroxide is added to raise the pH to about 9 or above as previously stated. Thereafter the material is filtered, washed and dried as before. Itwill be seen, therefore, that it is possible first to effect precipitation of ferrous dimethyl dithiocarbamate and thereafter react it with nitric oxide, or alternatively. to bring about the precipitation in the presence-of the nitric oxide and thereby form the ferric nitroso dimethyl dithiocarbamate in a single operating step. a v The invention'is illustrated by the. following examples in which the parts and percentages are on a..weight basis unless otherwise indicated.

EXAMPLE I The'reactants are as follows:

7 product and the results of the fungicidal activity tests are presented in the table below (Tests 1, 2 and 3).

Parts Moles Procedure B Procedure B differs from Procedure A in that the fer- (a) 40% sodiu in dimethy1dithiocarbamate 1,100 3.08 rous dimethyl dithiocarbamate slurry is first prepared. g3 ggz g g3 2}, The sodium dimethyl dithiocarbamate is diluted to a con- (d) Sulfuric acid (90%) 77.5 0. 70 centration of 5% in one vessel. In a separate vessel the (e) Sodium hydroxide (10%) 300 1O ferrous sulfate is added to water and sufiicient's lf l acid to aid in dissolving the ferrous sulfate and to give Procedure A a 10 to solutions The ferrous sulfate solution is The sodium dimethyl dithiocarbainate is diluted to a then added 9 the solutlfm Sodlun} dlmethyl dlthlo 5% aqueous solution and the sodium nitrite is added and carbalhate Wlth h h Y hght brown slurry stirred until dissolved. In a separate tank the ferrous 15 h hhialheh' The sohhhh hhme as a hqheohh sulfate is added to water and then the sulfuric acid is h 15 added to the y The.rema1mhg shlhmc h added so that an approximately 1O 15% Solution is is diluted to a 10% solution and 18 added slowly to ma ntained. The ferrous sulfate solution is then added slowi h PH the Slurry m the range from 5 to shrly with good agitation to the sodium dimethyl dithio- .cohhhhed for hour and a h green. product carbamate solution (77 F. reaction temperature). The 20 1S ohtalhed. H 15 checked Penodlcahy Wlth a H pH is checked using a pH meter after stirring 10 mina h g m the range 5 F. h utes to make certain that it is between 5 and 6. The g h e 15 h eh hddhd and the.shrnhg hgfi stirring is continued for 1 hour and the pH again measg hhhhtes ig g g controlling the PH W1 n ured. The sodium hydroxide is added in an amount to t 6 range preshh or mcedhre The colhr genbring the pH within the preferred range 9.5 to 11.0. erhhy turns to hghter shade ohgreeh upon addmg the The amount may vary within the range from 150 to 0 rsofhum h h' The Slurry 1S filtered and washed parts depending upon conditions. The pH is again meas- Yvlth water hmh 18 h of shlhate as Shown by checkured after stirring for 15 minutes. The reaction proceeds mg h hhrate Wlth hhrhhh h The prodin accordance with the following equation: uct is dried and ground as described in Procedure A. 30 The reaction conditions, yields and purity of product as 4(CH NC(S)SNa+2FeSO +3NaNO 2 r well as the results of the fungicidal activity tests are 2[ (CH NC(S)S] FeNO+ 3Na SO +NaNO +H O presented in the table below.

rnoonnunn A pH Temper Color 7 Tetralest No. u r e, Dried Amount methyl CHCla Yield Funglcidal Preclpi- After Product NaNOz Cpd., Insol. Activity tation NaOH Percent Addition 1 41 5.3 10.2 G 10 2.0 23.5 2 77 0.1 10.7 zuggi m- 10.7 13.1 231 iit lo 3 77 5.5 9.8 10- 10%xs- 11.8 13.9 230 300-500 4 77 5.7 10.0 "-00".-- 20%xs 12.0 11.2 240 300-500 5 77 5.4 10.8 do-.. Stolch1o 11.4 15.0 220 300-500 PROCEDURE B 6 77 5.2 10.8 Green... 107 xs. 7 1.8 17.8 200 7 95 5.0 10.2 "-00.--" 107:xs. 8.0 17.7 205 88 1 Theoretical yield 250. 1 Lowest p.p.m. to inhibit.

The slurry that has been formed is filtered and washed It will be noted that Test No. 6 which was carried out until the eflluent s sulfate-free'as determined by obby Procedure B produced a product that contained only seging riryppgcelcligtiasteifiorlmsfl1t26 a%din}g blariutm chloof ttiectlranietiigk llltlgiiuramfdissulfidde and, by t1}: sarrcile e i 1g er empera- 0 en, it i not e it an un 'ci al activit ccor t-ures being preferably avoided to minimize the danger ingly, various amounts raiiging from 5 to 50% tetraof spontaneous combustion, and it may thereafter be methylthiuram disulfide were added to the product and ground with Dry Ice. A number of products were made thoroughly mixed therewith. Tests of the fungicidal acfollowing the foregoing procedure and they were antivity were made on the mixtures and they were found alyzed by infrared techniques to determine the content to be substantially of the same order of fungicidal acof tetramethyl thiurarndisulfide. The amount of chlorotivity as products containing tetramethylthi'uram disulfide form insoluble material present was also measured. The formed in situ. Y products were tested for fungicidal activity using a stand- It is not essential that the process of the present invenard agar incorporation technique. tion be carried out precisely as described in the example. is Lies;oagladiiiiggpggtggrpgggeillueage gefst ohlenziical Essentieegly; the ferric nitroso dimethyl dlithiocarbamate is er er enre ar reactin in an a neon so ution containin ing is inoculated with Aspergillus niger by touching a hitr ic oxide (formed in the efiiampies from the sodiun i llogp of the fuliligus spores to the agar surface three times. nitrite and sulfuric acid), preferably in some excess, ap- 96 ehagar is t en incubated at 91.4 F. for a period of proximately chemical equivalent amounts of a water- L ours and observations are made for growth. A sesoluble dimethyl dithioearbamate and a water-soluble fer- ;iismof ICEFSeIIJ'ISIEIaSIOSrSS E1125)? fggpgigx igothpptmt 300 rlous salt}: afnd including the sterli1 (if Iiiailsing 11116 PH of thg I e es com- S urry o erric nitroso imet y it iocar amate we positions and the lowest concentration in parts per milabove the neutral point before filtering. Thus in place of lion of test compound needed to inhibit growth is deter sodium dimethyl dithiocarbamate there can be used potassium or other water soluble salts of dimethyl dithiocarbamic acid salts, and in place of the ferrous sulfate there can be used ferrous ammonium sulfate, ferrous chloride or other water soluble ferrous salts.

I claim:

1. The process of preparing ferric nitroso dimethyl dithiocarbamate which comprises reacting a dimethyl dithiocarbamate with ferrous salt and nitric oxide in acid liquid medium to form a slurry of ferric nitroso dimethyl dithiocarbamate in the liquid medium, increasing the pH of the slurry to at least about 9, filtering the solids from the liquid and washing the solids to remove soluble impurities.

2. The process of claim 1 wherein the pH of the slurry of ferric nitroso dimethyl dithiocarbamate is raised to a value in the approximate range 9 to 12 by the addition of an alkaline material before filtering.

3. The process of claim 2 wherein the pH of the slurry of ferric nitroso dimethyl dithiocarambate is about at the time of filtration.

4. The process of claim 1 wherein the pH of the acid liquid medium is in the range of 5 to 6.

5. The process of claim 1 wherein the ferric nitroso dimethyl dithiocarbamate slurry is formed by mixing an acid solution of a ferrous salt with a solution of a dimethyl dithiocarbamate and a nitrite with good agitation.

6. The process of claim 1 wherein ferrous dimethyl dithiocarbamate is first formed and thereafter treated in the form of an aqueous slurry with nitric oxide to form a slurry of ferric nitroso dimethyl dithiocarbamate.

7. The process of claim 6 wherein the pH of the slurry of ferric nitroso dimethyl dithiocarbamate is raised to a value in the approximate range of 9 to 12 by the addition of an alkaline material before filtering.

8. The process of claim 7 wherein the pH of the slurry of ferric nitroso dimethyl dithiocarbamate is about 10 at the time of filtration.

9. The process of claim 6 wherein the pH of the acid liquid medium is in the range 5 to 6.

10. The process of claim 5 wherein the pH of the slurry of ferric nitroso dimethyl dithiocarbamate is raised to a value in the approximate range 9 to 12 by the addition of an alkaline material before filtering.

11. The process of claim 10 in which the pH of the slurry of ferric nitroso dimethyl dithiocarbamate is about 10 at the time of filtration.

12. The process of claim 5 wherein the acid liquid medium formed by the mixing is in the range 5 to 6.

13. The process of preparing ferric nitroso dimethyl dithiocarbamate containing about 10% of tetramethylthiuram disulfide comprising the steps of reacting a dimethyl dithiocarbamate with a ferrous salt and a nitrite at room temperature in a liquid solution having a pH range of 5 to 6 to form a slurry of precipitated ferric nitroso dimethyl dithiocarbamate and tetramethylthiuram disulfide, increasing the pH of the slurry to at least about 9, filtering the solids from the slurry and washing the solids to remove soluble impurities.

OTHER REFERENCES Cambi et al.: Chem. Absts., vol. 26, page 41 (1932). 

1. THE PROCESS OF PREPARING FERRIC NITROSO DIMETHYL DITHIOCARBAMATE WHICH COMPRISES REACTING A DIMETHYL DITHIOCARBAMATE WITH FERROUS SALT AND NITRIC OXIDE IN ACID LIQUID MEDIUM TO FORM A SLURRY OF FERRIC NITROSO DIMETHYL DITHIOCARBAMATE IN THE LIQUID MEDIUM, INCREASING THE PH OF THE SLURRY TO AT LEAST ABOUT 9, FILTERING THE SOLIDS FROM THE LIQUID AND WASHING THE SOLIDS TO REMOVE SOLUBLE IMPURITIES. 